Daylighting films have been proposed for admitting sunlight into a building's interior, for example, through windows of the building. A typical daylighting film includes a light-transmitting support having formed on one of the faces thereof a plurality of unit prisms and a flat face. Sunlight is admitted into the interior through the unit prisms. One can guide external light into the interior to provide a brightly lit space, by attaching such a daylighting film to window glass.
However, if a special daylighting film is attached to a window, there may occur thermal cracking of the window glass. In view of this, Patent Literature 1 describes an insolation adjusting method in which rolling screen sheet materials (daylighting device) having insolation blocking properties are disposed at a distance from the indoor-side glass surface of wire-reinforced window glass.